Actually it is more like Forza 5-2=3
It is what FM3 was promised it was going to be.
Quick summary:
GT5 = visual superiority and photorealsim with driving model that is very good when coupled with a 3 pedal wheel and seat.
GT5 sounds = rubbish crap shit vacuums.
FM4 = acceptable visuals as far as XBox360 goes, not photorealistic but very good none the less with a driving model that is very good when couple with a 3 pedal wheel and seat.
FM4 sounds = glorious glorious booming and very real-like. Exclipse GT5 sounds by about 107 eyars of development time
Overall FM4 = GT5.
The one is let down by crap sounds th eother is let down by mediocre visuals.
Both drive very well and a great fun.
However, the sheer enjoyment of taking a 330P4 down the Mulsanne with the
CORRECT cacaphony of noises bellowing out the surround sound makes the FM4 65" HD driving experience a little better than the GT5 one.
For me, the bottomline is that if FM4 had GT5's visuals and track surface mapping it would be heaven -
almost no need for a real track day car
Almost...